The present invention relates generally to desk-top circular saws, and more particularly to an improved miter saw assembly having an extendible working surface for supporting a longer workpiece, wherein the sawing unit is vertically supported by a wheeled support assembly and a pair of telescoping arms enabling smooth longitudinal extension and retraction of the sawing unit during operation.
Motor-driven desk top circular saws, commonly referred to as compound miter saws, are well known cutting devices often used to perform both miter and bevel cuts. A disadvantage of such devices is that their maximum cutting length is limited by the diameter of the saw blade. This limitation requires the operator to reposition the workpiece in order to complete a cut longer than the diameter of the saw blade.
To overcome this disadvantage, compound miter saws have been provided with slide mechanisms so that the saw blade can be moved laterally of the workpiece to enable longer cuts to be made without repositioning the workpiece. Compound miter saws incorporating slide mechanisms for enabling longer cuts are disclosed in U.S. Pat. Nos. 4,869,142; 5,870,939; 5,768,967; 5,241,888 and 5,524,516. However, the disclosed slide mechanisms share a number of drawbacks and limitations.
A significant limitation of the aforementioned slide mechanisms is their restricted range of movement. For instance, U.S. Pat. No. 5,768,967 to Sasaki et al. and U.S. Pat. No. 5,870,939 to Matsubara disclose circular saw units slidably supported on a table by a slide mechanism including one or more slide bars extending into the table. In each case, the length of the slide bars defining the range of movement of the saw is limited by the size of the table into which the slide bars are received. U.S. Pat. No. 4,869,142 to Sato et al., U.S. Pat. No. 5,241,888 to Chen and U.S. Pat. No. 5,524,516 to Sasaki et al., each disclose a circular saw unit supported at a distal end of a slide bar mechanism. In each instance, the slide bar mechanism is extendible through a support whose position is fixed with respect to the table. As the slide bar mechanism is advanced, the weight of the circular saw unit causes a corresponding increasing bending moment about the support due to the cantilever type design. Consequently, the length of the slide bar mechanisms are necessarily limited to prevent undesirable bending of the slide bars, and corresponding downward movement of the saw unit, during a cutting operation.
Furthermore, the aforementioned patents disclose sliding mechanisms in which the sliding bars frictionally engage supporting structure as the saw unit is being slidably extended, making it difficult to maintain smooth, continuous movement of the saw unit while making a workpiece cut. In addition, the aforementioned slide mechanisms incorporate sliding bars having outer surfaces which remain exposed to the work environment during use. Consequently, dirt and other debris, including saw dust, may tend to adhere to the sliding bars and further impede the desired smooth and continuous sliding motion.
Accordingly, it would be desirable to provide a desk top circular saw incorporating a sliding mechanism overcoming these and other disadvantages and limitations of the prior art.
It is an object of the present invention to provide a table-top circular saw apparatus having telescoping arms enabling the saw unit to be extended and retracted to provide increased maximum workpiece cut lengths vis-a-vis known slidable circular saws.
It is another object of the present invention to provide a table-top circular saw apparatus including a rotatable workpiece support table having a cutting surface extendible in the saw cutting direction to accommodate the increased saw extension enabled by the telescoping arms.
It is yet another object of the present invention to provide a table-top circular saw incorporating a wheeled subassembly supporting the weight of the saw unit, thereby preventing bending of the telescoping arm members during extension thereof.
It is a further object of the present invention to provide an extendible saw apparatus having a wheeled subassembly including an internal level detection device restricting the downward extension of the assembly where the saw unit in an angularly rotated orientation with respect to the cutting surface.
It is still a further object of the present invention to provide a table-top circular saw apparatus incorporating a lock and key arrangement designed to prevent angular rotation of the saw unit unless the telescoping arms are in a fully retracted state.
These and other objects are achieved with the table top cutting apparatus of the present invention. Generally, an extendible compound miter saw assembly is provided comprising a base having a surface for supporting a workpiece to be cut, an angularly rotatable member extending from a rear end of the base, a saw unit subassembly mounted to a support block and vertically pivotal with respect thereto, a pair of telescoping arms attached at a near end to the angularly rotatable member and attached at a distal end to the support block, and a wheeled subassembly attached to the support block for supporting the weight of the saw unit subassembly and for enabling the saw unit to be extended and retracted during a cutting operation.
In an aspect of the invention, a retractable table extension subassembly is provide having means for being removably attached to a projecting portion of the base for supporting a long workpiece requiring an extended cut. Retractable table support legs are provided depending from the bottoms of the individual table extension members.
In another aspect of the invention, a latch mechanism is provided along with a key and lock subassembly for preventing extension of the saw unit when the angularly rotatable member is rotated with respect to the base.
In another aspect of the invention, a wheeled subassembly is provided having internal level detecting means restricting the subassembly from being lowered toward the workpiece support surface unless the wheeled subassembly is oriented substantially perpendicular to the underlying workpiece support surface.